The present invention pertains to a blade lock for blading a turbine of an axial design, with blades inserted into an undercut blade groove of the turbine rotor in a positive-locking manner, the blade groove being in connection with at least one mounting space and where a filler piece, which is in positive-locking relationship with a blade foot of the blades and a wedge are inserted into the mounting space. The present invention also pertains to a process for manufacturing a blade lock.
A blade lock for blading turbines, in which the rotor blades are inserted into an undercut blade groove of the turbine rotor extending in the circumferential direction in a positive-locking manner, has become known from DE-OS 30 28 701. At least one mounting space, into which a filler piece which is in positive-locking relationship with the foot of the blade is inserted, is provided on the circumference of the turbine rotor. The filler piece is pressed in tightly by a fitting piece, which is driven in between the wall of the mounting space and the filler piece. To increase the pressing force, the fitting piece is slotted, and a wedge is pressed into the slot during the driving in of the fitting piece into the mounting space.
In the prior-art blade lock, the pressing force acts on the foot of the blade and consequently on the turbine rotor via the fitting piece or the wedge. This may lead to warping and bending of the turbine rotor if the wedge has been driven in too tightly. The hot true running behavior of the turbine rotor may be adversely affected during the operation of the turbine, which may lead to an increase in the vibrations of the shaft.
The basic object of the present invention is to design the blade lock of this type such that no pressing force is exerted on the turbine rotor.
According to the invention, a blade lock for blading a turbine of an axial design is provided wherein the blades are inserted into an undercut blade groove of the turbine rotor in a positive-locking manner. The blade groove is in connection with at least one mounting space or mounting point and a filler piece which is in positive-locking relationship with the blade foot of the blades and a wedge are inserted into the mounting space. The cross section of the mounting space receiving the filler piece is conically widened beginning from the blade groove. The cross section of the filler piece is adapted to the cross section of the mounting space.
The side walls of the mounting space may be provided to extend at an angle to the blade groove. The side walls of the mounting space may be provided to form an angle (xcex11, xcex12) with the longitudinal axis of the blade in the axial direction. The wedge may be secured by stud screws in the turbine rotor.
According to another aspect of the invention, a process for manufacturing a blade lock as discussed above is provided. According to this process, after preparing the blade groove by turning, the filler piece, which has been prepared except for the blade groove contour, is inserted into the prepared mounting space and is fixed by a wedge. The blade groove contour is milled in the blade groove and at the same time in the filler piece. The filler piece and the wedge are removed from the mounting space. The turbine rotor is then equipped with the blades and the blades are secured in the blade groove by the blade lock.
The filler piece is held in the axial direction in the mounting space designed according to the present invention such that it is not pressed against the foot of the blade but is supported during the wedging in the mounting space in the turbine rotor. As a result, the warping force between the filler piece and the wedge no longer acts on the foot of the blade, and the axial pressing force is no longer passed through the blade groove. The turbine rotor is not subject to axial warping. The introduction of the blade lock cannot lead to bending of the turbine rotor during the manufacturing process. An adverse effect of a blade lock inserted too tightly on the hot true running behavior of the turbine rotor is ruled out. Each blade of a blade groove including the closing blade finds the same blade groove dimensions and clamping conditions.
The clamping of the wedged filler piece in the mounting space according to the present invention makes it possible to manufacture the blade lock according to the process, in which the contour of the groove of the filler piece and that of the blade groove are prepared in a common work mounting. This leads to a very high accuracy of fit of the filler piece and the wedge.
The present invention can be used generally for turbines of axial design operating as reaction or impulse turbines for steam turbines and process gas or tail gas turbines and especially for blade locks for blade feet of the hammerhead or double hammerhead design.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.